Elucidating Mechanisms of Chromatin Dysregulation by Oncohistones Project 2 will characterize the chromatin signaling pathways dysregulated by ?oncohistone? mutations and delineate the mechanism(s) by which aberrant chromatin landscape contribute to oncohistone-mediated tumorigenesis. With a combination of genetic, cellular biochemistry and (epi)genomic approaches, we will leverage and extend our preliminary findings to test a central hypothesis: Somatic mutations of histone H3 genes in multipotent stem cells alter normal pathways of polycomb complex deposition and genome-wide distribution, leading to significant changes in the transcriptome and epigenome that, in turn, promote tumorigenesis. Specifically, we propose to: 1) understand the chromatin deposition profiles of H3.3 G34 mutations and how they affect local chromatin environment; 2) investigate how global alterations in histone modifications by K-to-M mutations (H3K27M and H3K36M) are reflected at genome level and its impact on polycomb complexes re-distribution and gene expression; and 3) establish, genetically and pharmacologically, the importance of downstream histone methytransferases in tumor development and maintenance by oncohistones. Expected results will formulate novel theories and provide crucial mechanistic basis underlying the pathogenesis by oncohistones, which can be readily tested in in vivo cancer models (Project 1) and in vitro chemistry platforms (Project 3). To accomplish these aims, Project 2 also requires close interactions with both Cores.